The invention relates to a motor/transmission drive unit for a component movable between end positions. More particularly, the invention relates to a drive unit for driving an adjustable component such as a sliding roof in an automobile.
Motor/transmission drive units of the above-mentioned type require an end position recognition device, for switching the motor drive on and off when the adjustable component is in specific stroke positions, for example when the closing or opening end position of the component, e.g. the sliding roof of an automobile, is reached. For unequivocal recognition, the total stroke travel, which corresponds to a multiplicity of revolutions of the output shaft or drive shaft, must be converted, i.e. reduced by means of a reduction gear, into a maximum of one revolution of a countertakeup, or ratchet wheel, for actuating the motor switch.
German Patent DE-C1-42 09 652 discloses a drive device for a vehicle component adjustable between end positions. The electric motor of the drive device is connected via a reduction gear to a drive pinion which is seated on an output shaft and which is itself drive-connected to the adjustable component. Furthermore, the drive device includes a motor-controlling switching means for stopping the motor in at least one predetermined position of the adjustable component. A ratchet wheel for actuating the switching means is induced via an eccentric toothed gear to execute a rotational movement of less than 360.degree. during the adjustment of the component between its end positions. The eccentric toothed gear has an internally toothed outer wheel and an externally toothed inner wheel which is in meshing engagement therewith. The inner wheel is stationary. The outer wheel is mounted for a wobbling movement with respect to the axis of the inner wheel and forms the ratchet wheel cooperating with the switching means.
In motor/transmission drive units of the above-mentioned type, it is often desirable to have the additional possibility of manually operated emergency actuation; however, this is not provided in the case of the device discussed above.
A crankhandle-operable emergency drive of a drive unit otherwise capable of being driven operatively by means of an electric motor, in particular for sliding roofs in automobiles, is described, for example, in European Patent Application EP-A2-0 410 487. In this conventional unit, a releasable coupling connection is provided between the transmission, on the one hand, and a driveshaft of the drive unit, on the other hand, via a positive rotary takeup device. The outer face of the emergency actuation component has, in addition to a cylindrical portion, an axially extending externally hexagonal portion. This hexagonal portion is positively received in a corresponding hexagonal axial recess of the output gearwheel and of the output shaft, so that in normal operation a positive connection exists between the output gearwheel and the output shaft via the emergency actuation component. In the case of an emergency manual actuation operation, the positive connection between the emergency actuation component and the output gearwheel is broken by pressing the emergency actuation component axially forward against a prestressed helical compression spring. An end position recognition device is not provided in this conventional unit, however.